When I look Tiobe again, F# is #16.

http://www.tiobe.com/index.php/content/paperinfo/tpci/index.html

I get comments like

Looks like more academic work going on F# these days. Surprised to see Erlang or Haskell lagging behind so much on the ratings even though they are used heavily in the industry.

See more at: http://quantlabs.net/blog/2011/09/f-becomes-first-popular-functional-language-to-hit-top-20-according-to-tiobe-sorry-not-scala-clojure-haskell-or-erlang/#sthash.4V9xgLig.dpuf